Electron accelerator



Feb. 5, 1946.

W. F. WESTENDORP ELECTRON ACCELERATOR Filed Sept. 10, 1943 Fig. I.

Inventor: Willem F. Westendorp,

His

ttorney.

Patented Feb. 5,

rmc'rnou ACCELERATOR Willem F. Westendorp, Schenectady, N. Y., as-

slgnorto General Electric Company. a corporation of New York ApplicationSeptember 10, 1943, Serial No. 501,155

(on. sis-44) 4 Claims.

The present invention relates to apparatus for accelerating chargedparticles, such as electrons, by means of magnetic induction effects. I

Apparatus of the character referred to typically includes a closedvessel and a magnetic system for producing a time-varying magnetic fieldof such space distribution as to confine electrons projected within thevessel to a circular orbit along which the electrons are continuouslyaccelerated as the magnetic flux through the orbit increases ,inmagnitude. When the electrons have been accelerated to a high velocity,they may be diverted from the accelerating orbit and used for thegeneration of X-rays or for the production of other useful eflects.

Some of the difliculties encountered in the operationof an electronaccelerator are due to the accumulation of electric charges upontheinterior walls of the evacuated enclosure in which the accelerationof the electrons occurs. Such charges may be conducted away by aconducting coating applied to the inner surface of the evacuatedenclosure. It is difllcult, however, especially in a high-poweredapparatus, to provide a coating having sumciently high electricresistivity to prevent the generation of excessive 0 circulatory currenttherein.

In accordance with my present invention this dificulty has been overcomeby subdividing the conductive coating intoa number of sections connectedby external jumpers of high electric resistance. Circulatory currentsthen no longer are produced by the main magnetic flux. Such currents asare induced are produced by, the

much weaker flux traversing the boundaries of any one section.

The features which I desire to protect herein are pointed out withparticularity in the appended claims. The invention itself, togetherwith further objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawing, in which Fig. 1 is a partially sectionalized viewof an induction accelerator embodying my inventionyFig. 2 is a plan viewpartly in section of an annular electron chamber showing the highresistance connections between sectors of the chamber, and Fig. 3 is afragmental view of electrode structure.

Referring particularly to Fig. 1, there is shown in section a tubularglass vessel it closed on itself to provide a circular orbit in whichelectrons may be accelerated to a high voltage. The" vessel I0 ishermetically sealed and preferably highly to a vacuum pump (not shown).

The accelerating mechanism comprises a magnetic structure havingrotationally symmetrical (i.e. circular) pole tapered pieces ll, l2which are coaxial with the annular vessel It. These pole pieces areconstituted of laminated iron held in assembly (by means not shown), theoppositely facing central portions being of essentially planarcharacter. For decreasing the reluctance of the path between the opposedpole faces, there is provided an insert in the form of two laminatediron disks l3, id. An externally closed magnetic circuit between thebase portions of the pole pieces is provided by iron cores I 5, IS, ITand i8.

The magnetic structure is excited by means of a pair of series-connectedcoils l9 and 20 which surround the pole pieces I I and i2 and which areenergized in such manner as to produce a timevarying flux in themagnetic circuit.

' The coils i9 and 2b are connected in series with one another andacross a condenser (not shown) having such capacity as to resonate withthe inductance of the coils at a frequency corresponding to the desiredfrequency of operation of the apparatus. To supply the losses of theresonant circuit thus formed the coils i9 and 20 may be coupled toprimary windings 22 and 22' which are connected in series and energizedfrom an A.-C. power source, the connections not details of constructionand mode of operation of an electron accelerator of this type now arewell understood and are described in various prior publications.

Within the closed vessel ill (Fig. l) and also within the region ofinfluence of the magnetic field produced bythe pole pieces ll, l2 thereis provided a thermionic cathode 24 (Fig. 3) which, in connection with acooperating anode 25 serves to generate an intermittent stream ofelectrons.

Leading-in conductors 26 and 21 are indicated.

The electrode structure and other details of a typical electron'accelerator are described in an article entitled A 20-MillionElectron-Volt Betatron or Induction Accelerator by 0. W. Kerst.

in Review of Scientific Instruments, 'vol. 13

(1942), pages 307 to 394, and hence need not be 4 here described indetail.

My present invention is concerned with the accelerator chamber. As shownin Fig. 2 the accelerator chamber may be made up of a plurality tenorcoating is subdivided into zones.

of subdivisions as indicated. These are cemented to one another ingas-tight relation. The electrodes are introduced through a side tube28. The exhaust of the gas content occurs through a second side tube 29.

The interior wall of the annular: chamber is provided with coatings 30of silver or other suitable metal, as indicated by the stippling. Thecoatings are subdivided and the respective subdia visions are insulatedfrom one another by disfrom the conductive coatings of each section as 1indicated at 33. Between the respective conductors 32 are connectedresistances 36 of high value, for example of the order of 1000 ohmseach. Cir culatory currents through the respective coatings wouldencounter the sum of these resistances and hence could be only ofnegligible value.

What I claim as new and desire to secure by Letters Patentof the United'States, is:

1. An electron discharge device comprising-an annular receptacle ofnon-conductive material providing a chamber for'thepassage of electronstherein, a plurality of electrically distinct zones of conductivematerial on the interior 'wall of aid chamber, and conductors having amaterially higher resistivity than said zones respectively connectingsaid respective zones electrically to adjoining zones, thereby producinga highre sistance conductor which is substantially coextensive with saidannular receptacle.

2. An electron discharge device comprising an annular receptacleproviding a discharge space for electrons, a plurality of zones ofconductive material on the interior surface thereof, electricallyinsulated from one another, external electrical conductors for each ofsaid zones, and re: sistors connected between said cxtcrnalconductors toprovide a continuous circuit through said conductive coating.

3. An electron discharge device comprising a channel-shaped envelopeconsisting of a plurality of members of glass cemented to one another invacuum-tight relation, separate films oivmetal on the respectiveinterior surfaces of said members, electrical conductors extending fromeach of said films to'the exterior, and electrical resistances connectedbetween said conductors, said resistances having a value of the order 011000 ohms. v,

4. An electron discharge device comprising the combination of anelectromagnetic structure for producing a time-varying magnetic flux, are= ceptacle linked with said flux, consisting of nonconductive materialand providing a chamber for the acceleration therein of electrons, achargedissipating coating on the interior wall of said receptacle, saidcoating being divided into a plurality of distinct segments, highresistance conductors connecting said segments, thevresistivity of saidsegments and connecting conductors collectively being so high that onlynegligible rent is induced therein by said flux.

WIILEM- F. WESTENDORP.

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